How to Make a Soil Blocker

It’s seed starting season.  Yea!!

You can start seeds in any variety of containers.  People use everything from empty egg shells to the plastic six packs last years plants came in to just about any container laying around.  There comes a point at the beginning of the season when you have a lot of plants going and containers can get scarce.  Imagine if you didn’t have to deal with storing mounds of little plastic pots and just did without containers all together!  Well you can and the answer to your prayers is the soil blocker.  It compresses soil into…well…blocks.

Now you can buy a soil block maker.  They cost about 30 bucks from Johnny’s seeds but what’s the fun in that?   I decided to make my own.
You can too .
It’s not that hard.

Molly: I was skeptical when Mike told me about the soil blocker.  I mean, what holds them together?  I still don’t know but they work like a charm.

Mike: I love them.  It’s so easy to make a trayfull of blocks and get on with planting.  Plus when it comes time to transplant I just drop those babies right in the ground.

Soil Blocker

Building a soil blocker takes a few tools and building know-how but nothing insurmountable.

Lets get started!

Stuff You’re Gonna Need


About 2 feet of pine board 3/4″ thick  x 2″ wide

An 8″ piece of 4×4

About 2 feet of aluminum plate 1/8″ thick x 2 3/8″ wide

12 wood screws

1- 3/8″ carriage bolt  4″ long

1- 3/8″ nut & washer

Clear acrylic or varnish


Drill and bits

Table saw

Thin file

3/8″  tap

Start the Wood Frame

wood sides for soil blocker

Cut the 2″ wide stock into 3 pieces one at 8″ and 2 at 6″.

Cut a 45°angle on one end of each of the 6″ pieces.

Drill a hole in the center of the 8″ piece big enough to let the 3/8″ bolt pass through easily.

Now the Metal Frame Sides

Metal sides for soil blocker

Cut two 9 1/4″ long strips off the aluminum.
You can use the table saw for this.  It won’t harm the blade but go slow and be very carefull.

Drill and countersink two holes for the screws on each end of the pieces.

Mark a 1″ line at 2 5/8″, 4 5/8″ and 6 5/8″ on the long pieces.
Each line is centered on the width which leaves about 5/8″ space on either side.
Use a center punch to make a series of divots along the line.
Drill a series of 3/16″ holes along the line.
Use a file to turn the holes into a rectangular slot.

The Dividers

dividers for soil blocker

Cut three pieces at 2 3/8″ wide off the remaining aluminum.
Notch the ends so that they have tabs sticking out of each side.
The table saw and a file works well for this but again be careful.
The tabs are ~1/8″ deep and 1″ wide.  They should fit loosely into the slots.


Starting assembly of the soil blocker


Continuing assembly of the soil blocker

Screw one of the metal strips to the two wood sides.
The tapered ends should point down and face out.
Turn it all over and stand the dividers up in the slots of the lower metal strip.
You’ll need some bits of wood or another pair of hands to hold them up.
Place the other metal strip on top.  Make sure the tabs are aligned with the slots.
Screw the upper side to the wood sides.

The Plunger

Plunger for soil blocker

Plunger installed in soil blocker

Now we make the plunger from the piece of 4 x 4.
Make sure it fits loosely between the two wood sides.  If not make it so.
Cut one side off so that it is a little less than 2″ wide.  Again we want it to fit loosely inside of the cells of the blocker.
Cut 3 slots in it where the dividers go.  Make the slots wide enough to accommodate the dividers.
2 saw blade thicknesses should do it.
The slots should be about  2 3/4″ tall.
When you’re done the plunger should fit…you guessed it…loosely in the blocker.
Test fit it to make sure everything slides smoothly.

Finish the Assembly

Place the plunger in the blocker and tip it up.
Put the top bar of the frame on top of the plunger and use the hole in it as a guide to drill a hole for the 3/8″ bolt in the plunger.
Don’t go to deep.
Tap the hole in the plunger.

Screw the top bar of the frame into the top of the sides with two screws on each side.

Put the carriage bolt through the hole in the top bar.
Slide on the washer and screw on the nut leaving about an inch of the bolt sticking out.
Screw the bolt into the plunger and tighten the nut against it.
Slide the plunger up and down.
Is it working?

Clear Coat

clear coat on soil blocker

Take it apart and spray all the wood parts with a couple layers of the clear coat of your choice,
Once it’s good and dry put everything back together.

Use It

boc choi

The boc choi in the picture was planted last fall in a cold frame.  I just pulled it out of the ground and the block is still pretty much intact.  Pretty cool.

Now that you’ve built this contraption.  How do you use it?
It’s easy but you need a few supplies:

1. Moist potting soil / seed starting mix.  Don’t use garden soil.  Get the stuff in a bag.  Put it in a plastic bin and add water till it holds together in a ball when you squeeze it in your hand.

2. A shallow container.  I use a kitty litter pan.

3. A waterproof tray.  Something to hold the blocks in.  You want it to be waterproof so you can water the blocks from the bottom.

4. A spatula.  Good for moving the blocks around in the tray.

5. A pencil.  Works well for making holes in the blocks for seeds.

Making Blocks

Put some soil in the pan.  Make a mound about 1 1/2 times the height of the blocker cells.  It needs to be deep enough that it will compress as the blocker is pressed down but not so deep that the blocker can’t hit bottom.

Press the blocker into the soil and push down firmly all the way to the bottom.  Twist back and forth a little.

Take the blocker out and put it in the tray.  Press the plunger down as you pull the blocker up leaving the blocks behind in the tray.


You may find that you need to periodically clean the blocker as you are using it if it gets hard to work the plunger.

Now get out there and start planting!


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Here’s where else we are sharing Mike’s soil blocker:

Frugally Sustainable               Sumo’s Sweet Stuff               Happy Go Lucky

Making the World Cutter               Homesteaders Blog Carnival               Sew Chatty

Brassy Apple               Sew Can Do               Flamingo Toes

I’m Topsy Turvy               Tip Me Tuesday               Mommy By Day Crafter By Night

Sugar Bee Crafts               Today’s Creative Blog               The Thrifty Home

Lil’ Luna               Sew Much Ado               Oopsey Daisy

Under the Table & Dreaming               Someday Crafts               Somewhat Simple

Creations by Kara               A Glimpse Inside               Lady Bird Ln

Whipperberry               Sassy Sites               Thirty Handmade Days

Chic On A Shoestring



  1. Doglover1918
    Posted March 27, 2012 at 8:14 am | Permalink

    Great post!

  2. Jeff @ Sustainable Life Blog
    Posted March 27, 2012 at 9:50 am | Permalink

    those look awesome – any plans for people who cant cut aluminum as easy?

    • Posted March 28, 2012 at 9:10 am | Permalink

      Try hard plastic(plexi?) like Andrew suggested or maybe luan.(thin plywood).  Let me know if you end up making one.

  3. Posted March 28, 2012 at 4:10 am | Permalink

    Soil blocks are reportedly good stuff.  I haven’t used them, but I understand the principle. The roots of the seedlings don’t get stressed out going round and round a plastic container, but stop right there at the block edges, ready to plunge into the ground when planted. 
    I’ll have to get one, as I’m I’m not sure I could work on the aluminum.  Maybe use hard plastic instead?

    • Posted March 28, 2012 at 9:09 am | Permalink

      A bunch of people seem put off by working in aluminum.  It’s actually quite user friendly!  You can cut it with any woodworking tools.  Even a fine toothed hand would work.  I think it’s tougher to source it than to cut it.  Although I’ve noticed that street signs are just the right thickness.  I’m not suggesting anything but I’m just sayin’.

  4. Mike's Mom
    Posted March 28, 2012 at 8:10 pm | Permalink

    Nifty gadget!  Do you put the soil blocks, seeded but unsprouted, directly into your cold frame, or do you have to start them in your plant-starting station (laundry room)?  I could use one of these blockers, but only if no indoor plant-starting is necessary.  My cat likes to chew on my houseplants, so seedlings would look like perfect snacks to her.  Here’s a great gift idea:  you could give a blocker to your sister for her birthday, and I’ll borrow it (hee hee).

    • Posted March 30, 2012 at 8:58 am | Permalink

      Usually I wait until the second set of true leaves are up and then transplant into the ground or a larger pot.  I’ll keep the birthday idea in mind…

  5. Dennis12
    Posted March 29, 2012 at 6:53 pm | Permalink

    Great post! Last year I made a soil block maker but it was more complicated than this and not as sturdy. Maybe this weekend I can make one like you have designed. I don’t know where I can find aluminum. I have some galvanized roof flashing which is pretty thin but might work. Also, I may try adding a small wood handle to the top of the bolt. Seems like the head of the bolt will wear a hole in my palm after working with it for a while.
    By the way I first saw you post on Good job.

    • Posted March 30, 2012 at 9:03 am | Permalink

      Maybe if you folded the flashing in half and used it folded edge down to stiffen it.
      I had the aluminum left over from another project but I know it’s not easily sourced. Maybe
      Love to see the finished product or even a work in progress.  Post some pics here or go to our show and tell page.  It should be ready by Monday

      • Dennisboyd12
        Posted May 6, 2012 at 8:37 am | Permalink

         Well I finally got around to building the soil blocker. Because I didn’t have aluminum or a table saw I made a couple of adjustments. I used galvanized flashing and as you suggested I folded it in half – great idea. For the “pistons” I cut a 2×4 in half lengthwise (so they were about 1 1/2 x 1 3/4. Since they didn’t fill the 2×2 hole I made end caps out of the galvanized flashing I had (single layer not folded seems fine). A couple of additions were that I added a handle at the top and I dabbed some hot glue at the bottom of each end cap so there would be a dimple in the soil block. It works great, thank you very much for the design.
        By the way for anybody reading and choosing to go the galvanized flashing route, a pair of tin snips makes cutting a breeze. Also, I saw 3″ diatmeter x 36″ length galvanized sheet metal stove pipe in the big box stores for $3.00 that I think would work. Another point is if you go with the thinner “pistons” and make end caps be sure to tabs on the sides of the end caps.
        Anyway, thanks Mike and Molly for the great idea and clear instructions. Now that I have the hang of it I may make the little brother 1 1/2″ block version.

        • Posted May 6, 2012 at 8:50 am | Permalink

          I love the dab of glue from the hot glue gun to make the divets!  My next thought is tapping in upholstery tacks to create a divet- just another option.  Thanks for the photos!

        • Posted May 6, 2012 at 11:31 am | Permalink

          Great job Dennis!  I like the way the flashing came out and it’a a lot more accessible of a material. The steel caps on the pistons are a great idea too!

  6. Posted April 1, 2012 at 5:34 pm | Permalink

    Wow!  I can not believe the time and effort it must’ve took to make that soil blocker!  Very well done!  For those that just need to “plug and play” we sell the full line of dependable Ladbrooke Soil Block Makers and soil blocker supplies custom-tailored to the soil block gardening enthusiast.

  7. Oopsey Daisy
    Posted April 16, 2012 at 1:01 am | Permalink

    Great tutorial! Thanks for sharing at oopsey daisy! 

  8. Swanzguy
    Posted April 20, 2012 at 6:09 am | Permalink

    Hey that’s smart!  I bought the 3/4 inch and 2 inch block makers.  I would like to modify your idea to make a large 4 inch one.  hmmm?

  9. Stephen
    Posted February 21, 2014 at 8:42 am | Permalink

    Did anyone make a 4″ soil blocker? Whats out there for materials?

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